Implantable medical device

ABSTRACT

An implantable medical device is operable in a normal mode of operation, including a test mode, as well as in at least one other mode of operation outside of the normal mode. The device has a signal detector that is responsive to an external activation and a timer that can be programmed with a specified time period. If the external activation is detected by the signal detector during the programmed time period, the medical device is operated in a mode outside of the normal mode. The medical device enters into the test mode, within the normal mode, if the external activation is detected by the signal detector outside of the time period.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an implantable medical device accordingto the preamble of the independent claim.

2. Description of the Prior Art

It is known in the field of implantable heart stimulators or pulsegenerators to use a magnet to change the pacemaker to a predeterminedtest mode, for indication of e.g. battery condition. Other predeterminedmodes may for instance be threshold tests or diagnostic data storageetc. When such a test is performed a magnetically strong test magnet isheld at the skin of the patient in order to activate a detector. Anactivation of the detector results in a “magnet ON” detection, which inturn results in a change to the predetermined mode. Such a pacemaker isfor instance disclosed in U.S. Pat. No. 4,390,020.

U.S. Pat. No. 5,722,998 discloses an implantable medical deviceincluding a GMR sensor that inter alia is used to detect the presence ofa magnetic field from a permanent magnet. When a magnetic field isdetected the sensor causes the operation of the implantable device torevert to a magnet mode (also referred to as safe mode) of operation inwhich a predetermined, typically asynchronous, ventricular pacing rateis emitted.

However, some medical interventions might interfere with the function ofan implantable pulse generator such as a pacemaker. Examples areelectrosurgery, diathermal treatment etc. In these cases one possibilityis to program the IPG into a safe mode during the entire intervention.The device according to the '998 patent of course allows this, but atthe cost of not allowing the device to be provided with a magnet testmode, since the magnet mode is reserved for the safe mode. The deviceaccording to the '020 patent does not allow a safe mode, but does allowthe magnet test mode. To obtain a safe mode the device according to the'020 patent the device would have to be extensively reprogrammed by acardiologist both before and after the medical intervention.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an IPG that is moreflexible in regard of the magnet mode than the prior art discussedabove. It should be noted that, although the above prior art descriptionis based on magnetic signal detectors, the advantages achieved by theinvention encompass other signal detectors allowing a simple yes/no oron/off response to a signal.

The above object is achieved in an implantable medical device accordingto the invention having a mode control that operates components of theimplantable medical device in a normal mode that includes a test mode,as well in at least one other mode that is outside of said normal mode.The implantable medical device has a signal detector that is responsiveto an external activation and a timer that can be programmed with aspecified time period. The signal detector and the timer are connectedto the mode control, and if the external activation occurs during thetime period, the mode control operates the components in the mode ofoperation that is outside of the normal mode, and if the signal detectordetects the external activation outside of the time period, the modecontrol operates the components in the test mode within the normal mode.

The present invention offers the opportunity to customize the behaviorof an implantable medical device during a defined time period.

The new usage of applying the test magnet is that the magnet response isnot the normal specified test behavior during a specific period. Thefunction during magnet application will instead be what specifically hasbeen ordered. The specific period has a limited length that isdetermined during a programming session. After that specific period haspassed, the normal test behavior will occur upon magnet application,

It is known in the prior art that a device, e.g. an implantablepacemaker, may have different programmed magnet responses, but thefeature that after a predefined, limited tune period the specificbehavior will end and the device will revert to the normal magnetresponse behavior is not known in the prior art.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram of the present invention.

FIGS. 2-5 show time diagrams of three different scenarios thatillustrate different aspects of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a schematic block diagram of the present invention includingan implantable medical device 2 adapted to be operated in a normal modeof operation and in at least one other mode of operation and providedwith a signal detector 4 responsive of an external activation 6 from anexternal activation means 8. The signal detector 4 is preferably amagnetic sensor responsive of an externally generated magnetic field.The magnetic sensor may be e.g. a reed element, a GNIR sensor or a Hallsensor.

The medical device is provided with a special timer 10 adapted to beprogrammed with a specified time period (as indicated with the arrow12). The programming is performed by an external programming unit 14outside the body that communicates, e.g. via radio signals, with acommunication unit 16 in the medical device.

The medical device further includes a control unit 18 responsive for theoverall control of the function of the medical device. The differentparts of the medical device are energized by a battery means (notshown).

According to a preferred embodiment of the present invention the medicaldevice is an implantable heart stimulator, e.g. a pacemaker, acardioverter or a defibrillator. In this case the medical device alsoincludes a therapy means (not shown) adapted to generate a specifictherapy.

The medical device is adapted to enter a predefined special mode ofoperation if an external activation is detected by the signal detector 4during the specified time period, and the device is adapted to enter anormal test mode of operation if an external activation is detected bythe signal detector 4 outside the specified time period.

In the preferred embodiment where the medical device is a pacemaker anormal mode of operation may be a DDD mode, i.e. a dual chamberpacemaker provided with pacing and sensing capabilities in both heartchambers and having an inhibiting and triggering response to sensing.

If an external activation element 8, preferably a magnet is held at theskin 20 close to the medical device the mode of operation may be changedto a normal test mode.

As indicated above the normal test mode may be for example forindication of the battery condition, for initiating a test of thestimulation threshold or to start ECG recordings or other diagnosticdata storage.

The predefined special mode of operation is a safe operating mode wheretypically an asynchronous, ventricular pacing rate is issued. Theparameters used to define the safe operating mode and the specified timeperiod are preferably programmed and communicated to the communicationmeans during one and the same programming session before a medicalintervention.

The specified time period may in principle have any feasible value, buta practical upper limit may be a week and a lower limit may be in theorder of a few hours, e.g. 1 hour.

FIGS. 2-5 show time diagrams of three different scenarios thatillustrate different aspects of the present invention.

Each of the FIGS. 2-5 shows, from above, the detection signal in thenormal state (low) or in the detection state (high), and below followshorizontal bars representing the special time period, the normal mode ofoperation, the normal test mode of operation and the special mode ofoperation.

The signal detector 4 is adapted to generate a detection signal 22 (seeFIG. 1) that is set in a detection state upon the detection of anexternal activation and remains in the detection state as long as theexternal activation persists. The detection signal is normally in anormal state.

The specified time period is normally much longer than the duration forthe external activation.

In FIG. 2 the present invention is illustrated.

In a typical situation where the present invention is applicable thepatient is scheduled for e.g. a surgical operation involving some kindof procedure that could affect the functioning of the patient'spacemaker. The patient first visits his or her cardiologist, e.g. thesame day as the operation or some day before, who determines proper safeparameter settings, this being the special mode of operation, for thepacemaker during the surgical operation and also determines the specialtime period this setting should be used when an external activation isdetected by the signal detector 4. The cardiologist then programs thepacemaker with the determined parameter settings and the special timeperiod using the external programming means.

The special time period preferably starts to run immediately after thespecial timer 10 is programmed but could alternatively start to run apredetermined time after the programming is performed. This alternativesituation could happen if the patient visits the cardiologist on aFriday and the planned surgical operation is during the next week(Monday to Friday).

The patient then can undergo the planned surgical operation without thepresence of the cardiologist. During the critical part(s) of theoperation the surgeon/physician places a magnet on the skin outside thepacemaker that causes the pacemaker to enter the safe special mode ofoperation and to remain in that mode as long as the magnetic field isdetected by the signal detector 4. This is seen in FIG. 2 as thehorizontal bar representing the special mode that is activated when thedetection signal is in its detection state.

When the magnet is taken away the pacemaker returns to the normal modeof operation. In FIG. 2 the duration of the detection signal in thedetection state is, for illustrative purposes, much longer compared tothe duration of the special time period than in most actual situationswhen the invention is used.

FIG. 3 illustrates the behavior of the medical device if no special timeperiod has been programmed, i.e. the normal test mode is activated whenan external activation (the detection signal in a detection state) isapplied.

FIG. 4 illustrates the unusual situation that occurs if the special timeperiod runs out before the external activation is terminated. In thatcase the medical device remains in the special mode of operation enteredduring the specified time period even if the specified time period timesout, as long as the detection signal is in the detection state.

FIG. 5 illustrates a combination of the different scenarios shown inFIGS. 2-4 where a number of (three) activations are made, two within theduration of the special time period and one outside.

According to an alternative embodiment of the present invention theexternal activation are radio signals generated by the externalactivation means that may be included in the external programming unit.The radio signals being the external activation then includes asignaling message in the form of e.g. radio pulses coded to beinterpreted as activation, i.e. the detection signal is set in adetection state.

In this alternative embodiment the special mode of operation is ended byan external deactivation including a signaling message in the form ofe.g. radio pulses coded to mean deactivation.

According to another alternative embodiment the external activation hasthe form of light signals, either as continuous light or as activationand deactivation light pulses. The signal detector 4 is in thisembodiment any suitable optical sensor.

Although modifications and changes may be suggested by those skilled inthe art, it is the invention of the inventor to embody within the patentwarranted heron all changes and modifications as reasonably and properlycome within the scope of his contribution to the art.

1-15. (canceled)
 16. An implantable medical device comprising: a modecontrol that operates device components in a normal mode, including atest mode, and in at least one other mode outside of said normal mode; asignal detector, responsive to an external activation, connected to saidmode control; a programmable timer connected to said mode control, saidprogrammable timer being programmable to set a specified time period;and said mode control operating said device components in said othermode of operation outside of said normal mode if said externalactivation is detected by said signal detector during said time period,and causing said device components to operate in said test mode, withinsaid normal mode, if said external activation is detected by said signaldetector outside of said time period.
 17. An implantable medical deviceas claimed in claim 16 wherein said mode control is programmable,simultaneously with programming of said timer, to operate said devicecomponents in a safe operating mode as said other mode of operationoutside of said normal mode.
 18. An implantable medical device asclaimed in claim 16 wherein said timer is programmable to set said timeperiod to be less than five days.
 19. An implantable medical device asclaimed in claim 16 wherein said timer is programmable to set said timeperiod to be less than five hours.
 20. An implantable medical device asclaimed in claim 16 wherein said signal detector emits a detectionsignal in a detection state upon detection of said external activation.21. An implantable medical device as claimed in claim 20 wherein saidsignal detector continues to emit said detection signal in saiddetection state as long as said external activation persists.
 22. Animplantable medical device as claimed in claim 21 wherein said modecontrol maintains said device components in said other mode of operationoutside of said normal mode if said time period expires but saiddetection signal is in said detection state.
 23. An implantable medicaldevice as claimed in claim 16 wherein said timer begins said time periodsimultaneously with programming of said timer.
 24. An implantablemedical device as claimed in claim 16 wherein said timer begins saidtime period at a predefined time after said programming of said timer.25. An implantable medical device as claimed in claim 16 wherein saidsignal detector is a magnetic sensor responsive to an external magneticfield as said external activation.
 26. An implantable medical device asclaimed in claim 16 wherein said signal detector is an optical sensorresponsive to light as said external activation.
 27. An implantablemedical device as claimed in claim 16 wherein said signal detector is aradio signal detector responsive to radio signals generated by anexternal programmer that is also used to program said timer.
 28. Animplantable medical device as claimed in claim 27 wherein said signaldetector is responsive to a signaling message comprised ofelectromagnetic pulses coded to indicate activation, as said externalactivation.
 29. An implantable medical device as claimed in claim 28wherein said signal detector emits a detector signal in a detectionstate beginning with said electromagnetic pulses coded to indicateactivation, and ends said time period upon detection of a signalingmessage comprised of electromagnetic pulses coded to mean deactivation,by ceasing to emit said detector signal in said detection state.
 30. Animplantable medical device as claimed in claim 16 wherein said devicecomponents comprise components adapted to stimulate a heart.